Festergut - Tank Explodes at 10 Stacks of Gastric Bloat, But AoE Doesn't Affect Raid

The Problem:
During the Festergut encounter, when the tank reaches 10 stacks of Gastric Bloat, the tank dies as expected. However, the AoE explosion that should cause fatal damage to nearby raid members, leading to a wipe, is not occurring as intended. The AoE damage is either absent or minimal, allowing the raid to survive when it should wipe.

How it should work:
When a tank reaches 10 stacks of Gastric Bloat, they should explode, dealing massive AoE damage to nearby raid members and wiping the group.

How to reproduce:
Engage Festergut in Icecrown Citadel.
Allow the main tank to reach 10 stacks of Gastric Bloat without swapping tanks.
Observe that the tank dies but the AoE explosion does not cause fatal damage to raid members, as it should.

Character the bug occurred on:
[Insert Character Name Here]